|Mystery Rock found lurking in a Moroccan dealer's NWA box|
|Every year I paw through every box of NWAs I can find at Tucson. I don't pretend to be a meteorite expert; I mostly
just cherry-pick nice complete individuals with exemplary morphology. When I picked this one it was on precisely
that basis. Just a sweet little stone with what looked to be good regmaglypts, rounded shoulders, and a nice glossy
dark fusion crust. But, when I got home and re-examined everything, I found that this one didn't attract a magnet.
The specific gravity is about 2.985. The hardness is about 5.5 (will slightly scratch glass with difficulty; won't scratch orthoclase). There is no streak, but the grinding powder was light gray with a pale greenish hue. The piece weighed 20.15 gms before grinding a window. There are a few subtle hemispheric pits (note the one right below my thumb within what looks to be a regmaglypt). It contains no visible metal.
When this first caught my attention, I was convinced that, whatever it is, it is for sure a meteorite (an opinion based solely on external morphology and what looked to be a great glossy fusion crust). Now I am much less certain that it is a meteorite at all---BUT if it is, it has a chance to be something pretty special! Which is why I am asking for help--
My doubts arose after polishing a window (see below). That glorious polished surface is apparently not a fusion crust. It has no discernable thickness at all (and no flow textures or frothing, etc.).
|Every way you turn this stone, it has the look of a nice meteorite individual .|
|I polished a window on a chipped corner. The window measures about 1.4 cm left to right. Just barely visible to
the naked eye is a randomly oriented mush of rectangular to acicular lathes which I suppose to be plagioclase phenocrysts.
I can't resolve anything in the slightly greenish gray matrix. (It's not as green as this picture makes it look)
As a first guess, this is probably a basalt. And that would fit with the hemispheric surface pits being vesicles.
Note that what appears to be a glossy fusion crust is really just a surface polish. There is no discernable crust at the window edges.
Please let me know what you think. Just a fortuitously shaped, wind-polished chunk of terrestrial basalt? Or??? (I won't even say it!)
Thanks, Norm firstname.lastname@example.org
|Since you're here, I'd sure appreciate your thoughts on this little gem|
|There's no real doubt that this one's a meteorite, but check out that nice shock melt vein!Too bad it isn't a bigger piece (only 12.3 gms). A magnet is strongly attracted to this one, and both blebs of metal and chondrules can be discerned on the natural surface. There is almost no fusion crust.|
In this view it appears that a more irregular shock-melt engulfs breccia clasts. The melt vein of the previous image tracks across this side of the stone from the top edge of my thumbnail towards the lower part of my index finger.
My question is how rare is such prominent melt veining? Should I cut a couple of slices?
Thanks for your thoughts and advice,